A lighting system can be provided with a radar arrangement that is capable of detecting a moving object. Lighting is provided when a moving object has been detected. For example, UK patent application published under number GB 2 444 734 describes a street lighting system that provides illumination for objects passing along a roadway. The presence of objects is detected by one or more sensors, which may be in the form of motion detection radars.
A radar unit can detect a moving object in the following manner. The radar unit radiates a transmission signal at a given frequency. An object that is sufficiently close to the radar unit causes a reflection of the transmission signal, which the radar unit can receive. The reflection is multiplied by an oscillator signal having a frequency corresponding with that of the transmission signal. Accordingly, an intermediate frequency signal is obtained. In case the object that causes the reflection is moving with respect to the radar unit, the intermediate frequency signal will comprise an alternating current component. A peak detector, which is preceded by a capacitor, detects the alternating current component. The capacitor rejects a direct current component that would occur if the object were stationary. Accordingly, the peak detector provides an indication whether a moving object is within a given range, or not.